Lịch sử 100 năm thông gió nhân tạo - Drager

Heinrich Dräger receives his patent from the postman in the presence of his familyThe History of Ventilation Technology 13... The Control Principle of the Original PulmotorTo switch betw

It began with the Pulmotor

One Hundred Years of Artificial Ventilation

Ernst Bahns

Dräger Technology for Life®

It began with the Pulmotor –

One Hundred Years of Artificial Ventilation

Ernst Bahns

Table of Contents

Constant Progress in Intensive Care Ventilation: From the Spiromat to the EV-A 40

Respiration and Ventilation Technique: The Fundamental Difference 58

Simple and Open for Spontaneous Respiration: Pressure Controlled BIPAP 66

Optimum Pressure and Open for Spontaneous Respiration: Constant-Volume AutoFlow® 68

Trends in the Development of the Ventilation Process: Conclusion 82

Tendencies in the Development of the Ventilation Process: The Future 84

One Hundred Years of History

For Dräger, the history of ventilation is more than a soberchronological list – the history of ventilation is closely linkedwith the history of the Dräger family

The history of ventilation for the Dräger company starts withthe Pulmotor, for which my great-great-grandfather, HeinrichDräger, received the patent in the year 1907 In his memoirs

he describes how on a journey abroad he collected ideas forresuscitating people poisoned by gas and put these intopractice in the shape of the Pulmotor It was my great-grandfather, Bernhard Dräger, who helped prepare hisfather’s invention for serial production and developed theconcept of the Pulmotor controlled by airway pressure

My forefathers must have been committed to ventilation heartand soul, not simply confining themselves to managing thecompany They participated actively themselves in thedevelopment process I, too, have inherited this enthusiasmfor ventilation from my ancestors; I am a trained engineerand from 1999 to 2002 managed the worldwide businesssector for intensive care ventilation Today’s ventilators arecontrolled electronically by microprocessors

Preface 9

However, the objective of this brochure is not simply to tell

the history of ventilation, but we also want to contribute to

the discussion about the future of ventilation We want to

describe ventilation to you in such a way that not only medical

and technical experts will benefit, but everyone with an

interest in the subject can gain an insight and be able to

participate in the discussion about future trends in

ventilation

Having set ourselves the objective of bringing ventilation

closer to people who do not deal with it on a daily basis,

we have to explain some basics which others with a

grounding in the matter will already know For simplicity’s

sake, this booklet deals exclusively with ventilation within

the Dräger company

Stefan Dräger

Three professionals dedicated to ventilation

The history of ventilation is primarily the history of the people

at Dräger who were involved in it For many, ventilation wasjust about the sum of their life’s work To represent all thosewho contributed with creativity, industry and enthusiasm tomake ventilation at Dräger what it is today we have chosen

three colleagues from the Production, Marketing/Sales andDevelopment/Construction divisions Added together, their

years of dedication represent almost a century in the Drägerfamily concern

Hugo Hofmeister, born 1939, worked for more than

26 years as a fitter at Dräger He remembers the ventilators Spiromat, UV-1 and UV-2 both from

assembling the components and from end production

He was one of the so-called self-testers in the production team for the Evita ventilator who carried out the quality tests on the assembled devices.

11

Hans-Jürgen Klempau, born 1948, worked for 37 years in Sales and Marketing for emergency ventilation He started his career at Dräger selling the Pulmotor and organized the very first market launch for an Oxylog ventilator During his 10 years as head of the Emergency Medicine business division he was responsible for worldwide marketing of the Oxylog ventilators.

Dr Dieter Weismann, born 1942, started at Dräger as Project Manager for the development of the EV-A intensive care ventilator, the start of a career lasting

29 years As Head of Development he had a decisive impact on the first two generations of the Evita ventilator His contribution to innovation in the field of ventilation is proved by a dozen patents, primarily in the field of intensive care ventilation.

“Zero Hour” in Machine Ventilation –

The “Original Pulmotor”

Machine ventilation uses mechanical aids and oxygen to support insufficientspontaneous respiration A ventilator ventilates the lungs with a ventilation pattern,

a defined period of pressure and volume, thereby creating machine-supportedbreathing Ventilators must be equipped with a control method and generally useoxygen for ventilation

Hence two skills were required to develop ventilators The designers had to knowabout control principles and they had to be familiar with pressure gases Bothprerequisites were fulfilled at the beginning of the last century in the still veryyoung company of “Heinrich & Bernhard Dräger” and the development of aventilator was a top priority in the truest sense of the word

In his publication “The Development of the Pulmotor” (7) company founderHeinrich Dräger documented his ideas about developing a ventilator He described

a new technology for “blowing fresh air or oxygen into the lungs” His Pulmotor

created positive and negative airwaypressure alternatively and was powered

by oxygen under pressure In 1907Heinrich Dräger was awarded thepatent for developing his “originalPulmotor”

The original Pulmotor (1907) Protype of the

first Pulmotor that Heinrich Dräger patented

Heinrich Dräger receives his patent from the postman in the presence of his family

The History of Ventilation Technology 13

The Control Principle of the Original Pulmotor

To switch between inhalation and exhalation, Heinrich Dräger used a mechanism

in his original Pulmotor that he was very familiar with from his work as a skilledwatchmaker The ventilation pattern was controlled with a modified movementwith a cam disc

It is remarkable that Heinrich Drägerchoose this control principle of the

“Original Pulmotor” He selected atechnical principle which would replacenature as closely as possible By settingthe objective of imitating nature forartificial respiration, he was way ahead

of his time

For Heinrich Dräger, the physiologicalfunction that needed to be replaced was the regular movement of the lungswith a constant time pattern Therefore he selected a technical principle for hisventilator, guaranteeing a constant length of inhalation and exhalation duringartificial ventilation In modern terms, ventilation was time controlled

The rest of the world, as well as those who continued to develop the Pulmotorfurther, followed another principle Ventilation patterns were controlled by atechnical principle which switched between inhalation and exhalation when acertain ventilation pressure was reached These systems are pressure controlled.Pressure-controlled ventilation devices became more robust, more reliable andprecise - in short - technically improved Pressure-controlled ventilation devices seenfrom today’s point of view are technically optimized They followed a path which atthe time was more readily achievable technically

Bernhard and Heinrich Dräger

Heinrich Dräger

The History of Ventilation Technology 15

Here Heinrich Dräger was - ahead of his time Modern ventilators are not pressurecontrolled but are mostly time controlled However, we do not know whetherHeinrich Dräger knew then that his principle was closer to human physiology thanothers The fact remains that his Pulmotor, patented in 1907, signposted the waywith its timing control

Subsequent Development of the Pulmotor

by Bernhard Dräger

The “Proto-Pulmotor” was certainly a ground-breaking concept but it remained onthe level of a test model that was unsuited for practical use It had two faults whichHeinrich Dräger recognized and documented during development (7) Firstly hisconstruction caused considerable re-inhalation of exhaled gas Secondary thebreathing pattern could not be adapted to the patient due to the inflexible control ofthe movement Heinrich Dräger left it to his son Bernhard and engineer HansSchröder to find a remedy for these defects (8)

Bernhard Dräger solved the problem ofre-inhalation of exhaled gas by

redesigning the breathing connectingapparatus In the “original Pulmotor”the patient was connected to theventilator only by a tube This tubeworked to a certain extent as anextension of the windpipe since theinhalation and exhalation air was onlyseparated inside the ventilator

Bernhard Dräger replaced the connecting

apparatus of the “original Pulmotor” with a tube

system consisting of of an inhalation tube and

exhalation tube By alterating the valve control, the

patient’s inhaled and exhaled air could be

separated thereby greatly reducing the exhaled

carbon dioxide contamination of the inspiratory

air

Bernhard Dräger (1904)

Heinrich and Bernhard Dräger

Bernhard Dräger in the test workshop

The History of Ventilation Technology 17

From Prototype to the Production Line –

A New Control Principle

Another great challenge in developing the original Pulmotor was the disadvantage

of the rigid control system which could not be adapted to the patients’ lungfunction Dangerous ventilation pressures could arise, which are caused when the patient’s lungs are deteriorated Here the engineer Hans Schröder designed aconstruction using a control principle which would be used for several generations

of ventilators The newly designed control mechanism could be switched

automatically from inhalation to exhalation depending on the pressure in theairways A detailed description of the functional principle can be found on thefollowing double page

The answer to the question whichventilator was actually the first depends

on your point of view If you define aventilator as a machine which providesmechanically-supported breathing with a defined time pattern and offersthe possibility of ventilation usingoxygen, then Heinrich Dräger patented Pulmotor was probably the first in 1907

However, if you add the criteria of readiness for

production and proven success in clinical use,

then the development of the Pulmotor by Bernhart

Dräger and Hans Schröder should be considered as

the “first ventilator” From this point of view the

pressure-controlled Pulmotor was almost certainly

the first ventilator worldwide in the history of

Serial production of the Pulmotor

The History of Ventilation Technology 19

The Pulmotor Principle (1)

The Pulmotor was described in rough detail on the previous pages Now followsmore detailed description of the structure and function The technical innovations

of the Pulmotor are the “pressure and suction nozzle” to create the ventilationpressure and the control mechanism for switching between the inhalation andexhalation phases

The energy needed formachine-supportedventilation came from thecompressed gas cylinder ofthe Pulmotor, oxygen beingnot simply medicine for thepatient but also the source ofenergy for the ventilator The oxygen was mixed withambient air and fed via a

“suction nozzle” into a tubesystem The construction

of the nozzle can be seen in Heinrich Dräger’s diagram (7) When the compressedgas was fed in, gas flow was created in the tube system and positive pressure builds

up in front of the nozzle and negative pressure after the nozzle This type ofconstruction is called an injector

A valve system connected the patient during the inhalation phase to the positivepressure section in the tube system and in the exhalation phase with the negativepressure section The approximate airway pressures of the original Pulmotor laybetween +20 mbar in the inhalation phase and -20 mbar in the exhalation phase(7) The valve system for the original Pulmotor was a four-way cock which wasactivated by a movement as described above

Heinrich Dräger’s sketches of the original

Pulmotor perational principle (7).

Left: Inspiration, right: expiration

Schematic diagram of the pressure-controlled Pulmotor

The History of Ventilation Technology 21

The Pulmotor Principle (2)

In its subsequent development, the injector principle of the original Pulmotor wasretained by Hans Schröder However, the four-way cock and the movement werereplaced by a new control mechanism (See the details of the construction in thediagram on the next page)

The control mechanism consists of an inflatableleather bag which is connected to the tube system.This bag expands under positive pressure andactivates a control mechanism The controlmechanism in turn activates a valve system whichcauses a change to the gas flow in the respirationsystem In the “ON” position the patient isconnected to the positive pressure system andseparated from the negative pressure system Inthe “OFF” position the patient is separated fromthe positive pressure system and connected to thenegative pressure system

The valve system is still constructed such that the tube system is opened to ambientair during the exhalation phase so gas can flow out freely A so-called brakingbellows provides mechanical damping when switching between the respirationphases

Pulmotor with wall bracket

Pulmotor on tripod with additional device to add carbon dioxide to breathing air

for use in the operating theater

The History of Ventilation Technology 23

The Pulmotor Dispute (1)

Only five years after the start of production in 1908, 3,000 Pulmotors were in use –

an enormous number at that time (22) Ten years later, the number of Pulmotorshad doubled to almost 6,000 (12) and after 38 years the number was estimated atmore than 12,000 (16) The resuscitations performed with the Pulmotor weredocumented with meticulous exactitude by Drägerwerk and published with greatpride in the Dräger magazines (15)

There was a very obvious interest behind thispublicity activity by Dräger They wanted to prove tothe public that resuscitation via machine-supportedrespiration was superior to a manual method They defended themselves against criticism of theprinciple of high pressure respiration used in thePulmotor, a criticism which was levied by clinicalusers in the 1920s and came to a climax in the so-called “Pulmotor dispute” (13,14,16)

A Pulmotor, at the time, worked with a ventilation pressure of 20 mm H2O in theinhalation phase and a negative pressure of -25 mm H2O in the exhalation phase

To stimulate the respiratory center an admixture of CO2was used This meant that,with the exception of the ventilation pressure in the inhalation phase, ventilation atthe time differed considerably from methods today and the criticism of the clinic is

at least understandable from today’s point of view But the interesting thing is that

the dispute concentrated mainly on the supposedlydangerous effects of the ventilation pressure onheart and lungs – the much more questionablenegative pressures or the CO2admixture, as weknow today, attracted very little interest

Excerpt from the title page of

the first edition of the Pulmotor

News from 1929

Excerpt from the title page of a

Dräger brochure in 1917

Use of the Pulmotor at a bathing accident – contemporary drawing from 1913

The History of Ventilation Technology 25

The Pulmotor Dispute (2)

In 1922, the Department of Health as the then regulatory agency took the decision,based on the available knowledge, that there were no objections on health grounds

to the application of positive pressure ventilation However, it commissionedscientific investigations into the objections raised As we know, these investigationsinto the subject of “Damage to the organism from ventilators” have not come to aconclusion even today – so the “Pulmotor Dispute” is actually still relevant and thejury is still out

But the Pulmotor dispute isinteresting not only from thehistorical point of view.Another factor adds to theinterest, namely, the tacticaland strategic behavior ofDräger in the Pulmotordispute

In the Dräger magazines of the period (12,13,14), we can read about the effortsDräger undertook to dispel doubts about the efficacy of the Pulmotor and to counterconjectures about possible hazards These efforts went far beyond simple commercialinterests The company wished to prove that they were doing the right thing

Pulmotor used to save lives

So it was not just an issue of a product image, but rather a question of the company’sgood name This was defended against all parties; customers, associations,

regulatory agencies, and where appropriate, factual criticism was used as theimpetus to technical development

This strategy was more than “merchandising” as it was called at the time, today wewould call it marketing

Workers’ Samaritan Federation from Schlitigheim (Alsace) after a Dräger gas

protection course (1930)

The History of Ventilation Technology 27

Further Development of the Pulmotor –

The Pulmotor Canister

The Pulmotor principle with the switching mechanism using a bag, changedfundamentally in 1955 (11) Instead of controlling the breathing pattern via thedouble inflatable bag mechanism, a more manageable, smaller mechanism wasintroduced which was called the “Pulmotor canister” because of its casing

The switching mechanism in the Pulmotorcanister was so small that it could be taken out ofthe basic unit and attached close to the patient’sbody The two corrugated tubes, which were noteasy to handle and often became permeable overtime, were now superfluous The patient wasattached to the new Pulmotor via a 1.5 meter longpressure tube which improved mobility

considerably when using the new machine The spatial separation of Pulmotor canister and thebasic device meant the Pulmotor could be used inmany more applications and allowed for flexible use

of accessories For example, instead of the oxygeninsufflation unit a further Pulmotor canister could be attached to the basic apparatusand, when necessary, two patients could be ventilated using one basic apparatus.The ventilation pressures of the new Pulmotor

were +15 mbar for inhalation and -10 mbar for

exhalation compared to the values of the former

models The enrichment in the inspiratory gas,

which was available optionally in the previous

models as a supposed simulation of the patient’s

own breathing was no longer provided for

the new Pulmotor Instead, it was replaced by

a pneumatically-driven suction device

Backpack Pulmotor PT 1

Case Pulmotor PK2

Schematic diagram of the switching mechanism of the Pulmotor canister:

inspiration phase and expiration phase

The History of Ventilation Technology 29

Apart from the standard case version, which was introduced as the PK2 model, thesatchel version PT1 was also introduced The latter weighed only 13 kg, slightlymore than half the weight of the earlier cased version of the Pulmotor The PK 60and PT60 or PT61 models were enhanced models where a modified Pulmotor caseprovided pure oxygen ventilation without an intake of ambient air and for the firsttime made ventilation in a toxic atmosphere possible

The Pulmotor in Clinical Applications

For several decades the Pulmotor was an independent product series Its main area

of application was emergency resuscitation In addition, the Pulmotor principle wasused in various ventilation devices, mostly under another name

As early as 1910 the Pulmotor principle was used in the

“Dräger Ventilator type MOA” fitted with a switchingmechanism using a control bag and a simple airway gashumidifier In 1913 the Lung Gymnastic Apparatus Type MSAfollowed, fitted with a pedal to switch between the inspiratoryphases A mobile version of the Pulmotor was available asearly as the 1920s

The remarkable clinical version of the Pulmotor was thePoliomat which was fitted with the newly developed Pulmotorcanister as early as 1953 In contrast to the Pulmotors, whichwere developed for short-term use, the inspiratory pressure

in the Poliomat was not set in the factory but could bedetermined by the operator In addition, inspiratory frequencyand volume could be adjusted via control valves Both theinspiratory pressure and the ventilated volume could be readfrom the instruments The Poliometer was fitted with a inspiratory pressure meterand a volumeter

For conditioning the airway gas, Dräger used a

technique which was already used successfully for

mine rescues Nickel filter packages were used to

humidify the inspiratory gas The humidity in the

exhalation air condensed in the filters and this

condensate was used to humidify the inspiratory

gas in the inhalation phase

Lung Gymnastic

Apparatus Type MSA

for use in the

operating theater

(1913)

Operation of air moistener with nickel sieve

Portable Pulmotor on tripod with device for adding carbon dioxide (1928)

The History of Ventilation Technology 31

With the adjustment options for the inspiratory parameters, the measuring devicesand the inspiratory gas conditioning, the Poliomat was fitted with the most

important features of later intensive care ventilators However, the Poliomat with its Pulmotor principle faced competition from other types of apparatus in themarket to cover the enormous demand for ventilators after the Second World War

A New Way –

Alternating Pressure Ventilation with the Iron Lung

The great demand for ventilators for clinical applications was caused primarily bythe enormous increase in patients needing ventilation following the polio epidemics.The period shortly after the Second World War in particular saw a rise in thedemand for ventilators which could ventilate patients over longer periods of timeand in some cases were needed for lifelong use Various devices for this applicationwere developed which technically and operationally differed more or less from thePulmotor

One of these devices was a large, rigidcontainer into which the patient wasplaced Such an apparatus was calledsomewhat erroneously an “iron lung”.However, the term “iron chest” wouldhave been more accurate because therigid container acted as a secondthorax A flexible diaphragm ensuredcontinuous alternating pressure andventilated the lung like an artificialdiaphragm

With the iron lung the survival rate

increased markedly in cases of

respiratory paralysis following polio

A disadvantage was the amount of space

needed and the more difficult patient

care

Chest respirator (1956)

Iron lung installed in an ambulance (1954)

Iron lung model E 52 with electric drive (1952)

The History of Ventilation Technology 33

A further development of the iron lung was the thoracic ventilator where

alternating pressure was applied to the thorax only Dyspnea in newborn babies

is also treated in a negative pressure chamber that works on the same principle

as the iron lung

Creativity and Improvisation in the Post-War Period

The conditions in which the first iron lungs were designed and manufactured atDräger after the Second World War were initially very difficult Using exceptionallysimple resources and a great deal of improvisation, development was resumed atthe end of the war (6) A torpedo tube was adapted to function as a pressurecontainer for the prototype of the first iron lung The bellows of a forge was used for the ventilation mechanism and the motor came from a fishing boat

The pioneers of the post-war period who pieced together the first iron lungs themselves found a partner

in Dräger With decades of experience in developing rescue devices for mining and divingapplications, these engineers brought the concepts of alternatingpressure ventilation to the productionline

The first iron lungs mass-produced

by Dräger had a flexible diaphragm that could create respiratory pressures

of +25 mbar to -25 mbar These modelswere driven by water, with the E52model being the first to be electricallydriven

Iron lung with water drive (1950)

The first prototype of Iron Lung

Serial production of the iron lung at Dräger’s factory

The History of Ventilation Technology 35

Iron lungs were in use for a short time only because a new thrust brought about a

“renaissance” in positive pressure ventilation at the expense of alternating pressureventilators But this time the impetus did not come from the technical field butfrom clinical applications

The Beginning of Intensive Care Ventilation –

Assistors

In the 1950s, a new perception in clinical investigation brought about a newattitude in ventilation therapy Faulty treatment and complications were frequentlycaused because medical staff had to rely more on subjective clinical impressionswhen assessing ventilation rather than exact measuring parameters (5)

Without knowing the exact respiratory volumes administered, the set volumes couldinjure patients Either patients suffered from inspiratory gas insufficiency or theywere exposed to high stress by unnecessary intensive care ventilation

New findings, in particular fromScandinavia, led to positive pressureventilation with its superior ventilationcontrol becoming important once more Two lines of thought werefollowed: Firstly the volume ofinspiratory gas was monitored inpressure regulated ventilation

Secondly a constant preset breathvolume was applied

For these new application areas, Dräger developed ventilation apparatus both forpressure regulated and contstant-volume regulated ventilators which existed side

by side for a time In the field of pressure-regulated ventilation, the Assistor seriesdeveloped further the successful principle of the Pulmotor (10)

A common characteristic of the Assistors, apart from pressure regulation, was thepossibility to assist spontaneous respiration, i.e., the patients could initiate

mechanical breaths with their own attempts at spontaneous breathing In additionthe volume could be monitored in all assistors and aerosols administered via anintegrated atomizer connection

The Assistor 640 basic device made spontaneous respiration possible which wasintensified with machine support The later models offered controlled respirationwhere the number of machine-assisted breaths could be set

Assistor Model 642 (1966)

1960 1965 1970

Assistor 744

Assistor 644

Assistor 642

Assistor 641

Assistor

640

Assistor device range for pressure-controlled ventilation

The History of Ventilation Technology 37

The timer on the Assistor 641 was pneumatically driven; in the Assistor 642, it waspowered by electricity With the Assistor 644, the length of use was extended with

a new system of inspiratory gas humidification and the circle of patients extended

to pediatric applications The Assistor 744 improved ventilation quality, in particular

in pediatric applications, with a more sensitive trigger mechanism which meanteasier activation of machine-assisted respiration Furthermore, the appearance ofthe early assistors, which took some getting used to, was changed dramatically

A user-friendly but esthetic product design was becoming increasingly importantwhen developing medical equipment

The Road to Modern Intensive Care Ventilation

The assistors extended the area of application of ventilation considerably Inaddition to ventilation for polio patients, post-operative ventilation and inhalationtherapy for chronic lung disease became common Despite the expansion of therange of applications, machine-assisted ventilation remained a relatively simplemeasure

However, modern ventilation goes one step further It does not function simply as a bridge during a period ofrespiratory insufficiency, rather itadapts the type of ventilation to thecause of the dysfunction and wherepossible treats the dysfunction in atargeted manner Modern ventilation isrespiratory therapy

The requirements of targeted intensive therapy

meant new demands on ventilators In particular

users were looking for control over the ventilation

volume Furthermore, the length of ventilation

time should be variable by adjustable parameters

and not simply be dependent on the lung

mechanics of the patient Time-controlled,

constant-volume ventilation was required

The first Dräger ventilation devices which fulfilled

these requirements were the Spiromat series,

introduced in 1955 They marked the starting

point in the development of modern intensive

ventilator equipment at Dräger

Spiromat 661 with ventilation head E for long-term ventilation

of adults Spiromat in clinical use

Ventilation of a patient after tracheotomy with the Spiromat 661

The History of Ventilation Technology 39

Constant Progress in Intensive Care Ventilation – From the Spiromat to the EV-A

The next generation of ventilators were the UV-1 “Universal Ventilator” introduced

in 1977 and the UV-2 They adopted conventional bag ventilation from the Spiromat,whereby the inspiratory gas is sucked out of a bag and pressed into the lungs.Control and monitoring of these devices was already performed electronically

In 1982 the EV-A “Electronic Ventilator” introduced a completely new valve

technology to Dräger ventilators Electromagnetically actuated valves allowed theinspiratory gas flow and the inspiratory pressure to be controlled precisely andrapidly even during a breath Microcomputers were able to create respiratorypatterns which were unthinkable with the previous generation of equipment

In addition, the EV-A series was the first to offer graphic monitoring ofrespiration Respiration curves,numeric data and text messages couldall be displayed on a screen integratedinto the ventilation device Since thengraphic monitoring on an integratedscreen has been a standard feature

of Dräger intensive care ventilationdevices This integrated graphicmonitoring was introduced by othermanufacturers 15 years later and fromthat date became part of the basicconfiguration of intensive careventilation equipment

Intensive ventilation with UV-1

The movement of the ventilation bellows is

observed by the user to detect breathing

phases